The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 198 01 891.6, filed on Jan. 20, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a press section of a machine for producing a fiber material web, e.g., a paper and/or cardboard web, and a process for guiding the fiber material web through the press section. The press section includes at least two double-felted presses in series.
2. Discussion of Background Information
Press sections similar in general to the above-noted press section are utilized to drain fiber material webs, and include shoe presses formed with a concave contact pressure surface to form an elongated press nip (gap) with a cylindrical mating roll. Such press nips can significantly improve drainage performance.
However, because of the high water content of the fiber material web, problems arise in removing the water pressed out in the first, or upstream, press nip.
The present invention provides a simply structured press section having improved drainage in the first, i.e., upstream, press nip relative to a web travel direction.
The present invention provides an upstream press nip, ie., relative to the web travel direction, formed by a deflection-adjustment shoe roll and a suction roll.
The shoe press rolls may be generally formed of a flexible press jacket guided over or across a press element having concave contact pressure surfaces. This arrangement permits an elongated press tip to be formed with a cylindrical mating roll. In this manner, the fiber material web in the press nip is exposed to press pressure over a longer distance and, therefore, is more intensely drained Additionally, the pressure in the press nip is not started abruptly, rather, the pressure can be raised continuously, e.g., from a low value to a higher value.
Drainage felts may be positioned on both sides of the fiber material web to provide adequate capacity for absorbing the water pressed out of the fiber material web, and even-sidedness of the fiber material web. Moreover, by utilizing a suction roll in the upstream, or first, press nip, the absorption capacity for the water pressed out of the fiber material web may be significantly increased.
Particularly at high speeds, it may be advantageous for the fiber material web to be supported by at least on belt, sieve (screen), felt, or similar device, starting from the transfer from an upstream unit until delivery to a downstream unit. This leads to secure guidance of the web and thereby reduces the frequency of web breakages.
Additionally, drainage performance of the press section can be further improved if the double-felted press nip positioned downstream, i.e., in web travel direction, is formed at least by one deflection-controlled roll, e.g., a shoe press roll. In this manner, it is possible to limit the press section to two press nips, which reduces cost considerably.
Guidance of the fiber material web can be achieved by one drainage felt of the press nip. It may be particularly advantageous in this case for a drainage felt of the first press to take off the fiber material web from an upstream sieve (screen) section and for the drainage felt, located on the other side of the fiber material web, of the downstream press to take off the fiber material web from the drainage felt of the first press, and transfer it to the downstream drying section.
To ensure secure guidance of the web and to reduce remoistening of the press nip, it may be further advantageous for the drainage felt of the first press that guides the fiber material web to run around the suction roll.
Accordingly, the present invention is directed to a press section of a machine for producing a fiber material web. The press section includes at least two double-felted presses arranged in series in a travel direction of the fiber material web. An upstream one of the at least two double-felted presses may include a deflection-controlled shoe press roll and a suction roll, and the deflection-controlled shoe press roll and the suction roll may be arranged to form an upstream press nip.
In accordance with another feature of the present invention, the at least two double-felted presses may be arranged such that the fiber material web is supported by at least one support belt between a transfer point from an upstream unit to a transfer point to a downstream unit. Further, the at least one support belt may include at least one of a belt, sieve, and felt.
In accordance with still another feature of the present invention, the press section may include only two press nips. Further, the at least two double-felted presses may be arranged such that the fiber material web is supportably guided through the press section by at least one drainage felt. Further, a drainage felt of the upstream press may be adapted to receive the fiber material web from an upstream sieve section and a drainage felt of a downstream one of the at least two double-felted presses, arranged on a side of the fiber material web opposite the drainage felt of the upstream press, may be adapted to receive the fiber material web from the drainage felt of the upstream press and to transfer the fiber material web to a downstream drying section. Further, the drainage felt of the upstream press may be adapted to guide the fiber material web around the suction roll.
In accordance with a further feature of the present invention, the fiber material web may include at least one of a paper and cardboard web.
The present invention is also directed to a process of guiding a fiber material web through a press section of a web producing machine that includes at least two double-felted presses arranged in series in a travel direction of the fiber material web. The process may include guiding the fiber material web through a press nip of an upstream one of the at least two double-felted presses formed by a deflection-controlled shoe press roll and a suction roll.
In accordance with another feature of the present invention, the process may further include supporting the fiber material web by at least one support belt between a transfer point from an upstream unit to a transfer point to a downstream unit. Further, the at least one support belt may include at least one of a belt, sieve, and felt. The process may also include continuously supporting the fiber material web by at least one support belt between a transfer point from an upstream unit to a transfer point to a downstream unit.
In accordance with still another feature of the present invention, the process may further include guiding the fiber material web through a downstream one of the at least two double-felted presses, which is composed of a deflection-controlled roll.
In accordance with a further feature of the present invention, the process may further include guiding the fiber material web through only two press nips in the press section. Further, the process may further include supportably guiding the fiber material web through the press section by at least one drainage felt. Further, the process may further include receiving the fiber material web on a drainage felt of the upstream press from an upstream sieve section, receiving the fiber material web on a drainage felt of a downstream one of the at least two double-felted presses, which is arranged on a side of the fiber material web opposite the drainage felt of the upstream press, from the drainage felt of the upstream press, and transferring the fiber material web to a downstream drying section. Still further, the process may further include guiding the fiber material web around the suction roll on the drainage felt of the upstream press.
In accordance with yet another feature of the present invention, the fiber material web may include at least one of a paper and cardboard web.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.